This realizes the metadata source via the default hint to provide backward-compat with Maven 2.x whose Plexus version
registered component descriptors twice: once keyed by role+roleHint and once keyed by role only.

The code in this class is taken from DefaultRepositorylayout, located at:
http://svn.apache.org/viewvc/maven/components/trunk/maven-artifact/src/main/java/org/apache/maven/artifact/repository/layout/DefaultRepositoryLayout.java

Get flags this Mojo as requiring the dependencies in the
specified class path to be resolved before it can
execute: compile,
runtime, test,
compile+runtime (since Maven 3.0)
or runtime+system (since Maven 3.0).